Important role of chemical interaction on flame extinction in downstream interaction between stretched premixed H2-air and CO-air flames

Important role of chemical interaction in flame extinction is numerically investigated in downstream interaction among lean (rich) and lean (rich) premixed as well as partially premixed H₂- and CO-air flames. The strain rate varies from 30 to 5917 s⁻¹ until interacting flames cannot be sustained anymore. Flame stability diagrams mapping lower and upper limit fuel concentrations for flame extinction as a function of strain rate are presented. Highly stretched interacting flames are survived only within two islands in the flame stability map where partially premixed mixture consists of rich H₂-air flame, extremely lean CO-air flame, and a diffusion flame. Further increase in strain rate finally converges to two points. It is found that hydrogen penetrated from H₂-air flame (even at lean flame condition) participates in CO oxidation vigorously due to the high diffusivity such that it modifies the slow main reaction route CO + O₂ → CO₂ + O into the fast cyclic reaction route involving CO + OH → CO₂ + H. These chemical interactions force even rich extinction boundaries with deficient reactant Lewis numbers larger than unity to be slanted at high strain rate. Appreciable amount of hydrogen in the side of lean H₂-air flame also oxidizes the CO penetrated from CO-air flame, and this reduces flame speed of the H₂-air flame, leading to flame extinction. At extremely high strain rates, interacting flames are survived only by a partially premixed flame such that it consists of a very rich H₂-air flame, an extremely lean CO-air flame, and a diffusion flame. In such a situation, both the weaker H₂- and CO-air flames are parasite on the stronger diffusion flame such that it can lead to flame extinction in the situation of weakening the stronger diffusion flame. Important role of chemical interaction in flame extinction is discussed in detail.     

Defect/Edge‐Selective Functionalization of Carbon Materials by “Direct” Friedel–Crafts Acylation Reaction

Popularly utilized oxidation media, via nitric acid/sulfuric acid mixtures, are too corrosive and oxidizing to preserve structural integrity of highly ordered graphitic materials (carbon nanotubes (CNTs) and graphene). Here, for the most commonly used oxidation method, the important advantages of defect/edge‐selective functionalization of carbon materials (CNTs/graphene/graphite) in a polyphosphoric acid (PPA)/phosphorous pentoxide (P₂O₅) medium are elucidated. The optimized PPA/P₂O₅ medium is a mild acid that is not only less corrosive than popularly utilized oxidation media, but also has a strong capability to drive Friedel–Crafts acylation by covalently modifying carbon materials. With a broader spectrum of functional groups accessible, the PPA/P₂O₅‐driven Friedel–Crafts acylation offers more options for tailoring the properties and processing of carbon materials.     

Modelling and analysis of pre-combustion CO2 capture with membranes

A pre-combustion CO₂ capture system was modelled with three different membranes. It comprised an amine absorber for the elimination of H₂S, high- and low-temperature water gas shift reactors for the conversion of CO to CO₂ and a membrane to keep over 90% of the CO₂ in the retentate. The absorber and equilibrium reactors were modelled using rigorous models, while the partial least squares model was used for three different types of membranes to predict the experimental results. The effectiveness of the modelling of the reactors and membranes was tested through comparison of simulated results with experimental data. The effects of operating pressure and membrane type are also discussed, and it was found that using a smaller membrane under high pressure lowered the membrane’s cost but also lowered energy recovery.     

Flavonoids from the fruits of Nepalese sumac (Rhus parviflora) attenuate glutamate-induced neurotoxicity in HT22 cells

Nepalese sumac (Rhus parviflora) is a wild edible fruit used for the treatment of various ailments including neurological complications and stomach disorders in the traditional medicinal system of south Asia (Ayurveda). Four flavonoids were isolated from ethyl acetate (EtOAc) fraction of Nepalese sumac fruits and their chemical structures were determined on the basis of NMR, fast atom bombardment mass spectrometry (FAB/MS), and IR. The efficiency of isolated compounds in attenuating glutamateinduced cell death in an immortalized mouse hippocampal cell line (HT-22) and inhibition of cycline dependent kinase 5 (Cdk5) were investigated. Among the compounds, flavanols, fustin (1) and taxifolin (2), an aurone, aureusidin (3), and a biflavonoid, agathisflavone (4) were found to have protective effect against glutamate induced oxidative injury in HT22 cells. Aureusidin (3), a Cdk5/p25 inhibitor (IC₅₀ 3.5 μM), was the most potent neuroprotector with an EC₅₀ value of 11.90 μM.     

Effect of Rubus coreanus Miquel on prostate tumour growth

The rapidly increasing incidence of prostate cancer in Korea has increased awareness of preventive measures, such as dietary supplementation. Unripe Rubus coreanus Miquel (RCM) has been used to improve prostate health. Using nude mice transplanted with a prostate cancer cell line, we investigated whether RCM supplementation was beneficial for inhibiting the formation or growth of prostate tumour, and its mechanisms. RCM effectively restricted tumour growth compared to the control but had no effect on tumour initiation. Ripe and unripe RCM exerted significant reduction in tumour growth compared to the control. The reduction in tumour mass shown in the RCM groups was associated with increased active form of caspase-3, indicating an enhanced caspase-3-mediated apoptotic process. In addition, RCM demonstrated a strong antioxidant capacity through a decrease in lipid peroxidation products. In addition, RCM modulated the activity of endogenous antioxidant enzymes through modest changes. Collectively, our data indicate that RCM is a promising alternative supplementation for limiting the growth of prostate cancer, and its effect is likely to be achieved through the initiation of caspase-3-mediated apoptosis. The antioxidant properties of RCM appear to play an essential role in its anti-proliferative effect on prostate tumours.     

Development of an uncertainty quantification method of the best estimate large LOCA analysis

A statistical uncertainty quantification methodology for evaluation of the emergency core cooling system (ECCS) performance is proposed and applied in assessing the best-estimate peak cladding temperature (PCT). In the proposed methodology, the Latin hypercube sampling method is adopted, and separate model uncertainties are used as input variables. The independency of the input variables is verified through a correlation coefficient test for statistical treatment of their uncertainties. Next, the PCT response distribution is determined through a goodness-of-fit test. Finally, the PCT with a one-sided 95% probability and a confidence level of 0.95 is estimated.This methodology is applied to the large-break loss-of-coolant accident (LBLOCA) of Kori Nuclear Units 3 and 4. This study shows that the proposed methodology is a useful one.     

Removal characteristics of anionic metals by micellar-enhanced ultrafiltration

Surfactant-based separation of Fe(CN)(6)(3-) and CrO(4)(2-) using regenerated cellulose membrane was studied in order to assess the potential of micellar-enhanced ultrafiltration for the remediation of wastewater or groundwater polluted with ferriccyanide and chromate. In the ferriccyanide/octadecylamine acetate (ODA) and chromate/ODA systems, removal of ferriccyanide increased from 73 to 92% and to 98%, and that of chromate from 64 to 97% and to >99.9% as the molar ratio of ODA to ferriccyanide and to chromate increased from 1 to 2 and to 3, respectively. In the ferriccyanide/chromate/ODA system, while the removal of ferriccyanide increased from 62 to 72% and to 93%, the removal of chromate from 20 to 38% and to 68% as the molar ratio of ferriccyanide:chromate:ODA increased from 1:1:1 to 1:1:2 and to 1:1:4, respectively. With the molar ratio of 1:1:6, the removal was >99.9 and 98% for chromate and ferriccyanide, respectively. Ferriccyanide ions were more easily bound to ODA micelles because the binding power of ferriccyanide was greater than that of chromate.